The present invention relates to chairs in general, and to office chairs in particular.
Chairs are known to comprise, for their support on the floor, a structure carrying a seat and a back-rest. The position of their seat relative to their back-rest is fixed in the direction from the rear to the front.
The inventor of the present invention has realized that it would be very useful to conceive a chair in which the seat can be advanced relative to the back-rest in said rear-front direction (hereinafter known as the advancement direction) within a predetermined range, starting from an initial withdrawn position. It has in fact been verified that this enables greater comfort to be offered to the user, in addition to enabling the position of the seat relative to the back-rest to be adapted to the specific physical characteristics of the user, so that this latter can assume a more correct posture.
It should be noted that in the present case an inventive level is recognizable in the first place from the fact of having become aware of this requirement, i.e. of having posed the problem.
The object of the present invention is therefore to provide a chair in which the seat can be made to advance relative to the back-rest. This object is attained by the chair according to the present invention, characterised by being provided with a mechanism which enables the seat to be advanced relative to the back-rest, within a predetermined range.
Specifically, this mechanism comprises:
a connecting rod means which connects the rear of the seat to the support structure, the connecting rod means operating in a vertical plane parallel to the advancement direction;
an intermediate element disposed between the seat and the support structure, and which at its rear also carries the back-rest;
guide means which enable the seat to be moved in the two senses along the advancement direction, relative to the intermediate element;
a cylindrical hinge means with its axis horizontal and perpendicular to the advancement direction, which secures the intermediate element to the front part of the support structure;
a rearward-located elastic means which tends to withdraw the intermediate element from the support structure.
A user sitting on a chair provided with the mechanism, the essential characteristics of which are described above, can comfortably adjust the advancement position of the seat relative to the back-rest by simply pressing against the back-rest with his or her body, until the seat assumes the desired advancement position. To maintain the advancement position reached by the seat in this manner, the user has merely to abstain from further pressing his or her body against the back-rest.
From the aforegoing description of the characteristics of said mechanism, it will be apparent that as the back-rest is carried by the intermediate element, when this latter rotates about the said hinge means, the back-rest also undergoes an identical rotation about the same hinge means, without however undergoing translational movement.
Preferably, in order to achieve greater solidity of the advancement mechanism and a better force distribution, the said connecting rod means comprise a pair of parallel, spaced-apart connecting rods, the corresponding end hinges of which are coaxial.
The aforesaid elastic element is conveniently a helical spring. Preferably, elastic means are provided to automatically return the seat into its most withdrawn position when the chair is unoccupied by the user.